One system that may be assembled to form a hybrid vehicle is described in U.S. Pat. No. 6,554,088. This system presents an internal combustion engine having a turbo charger that is part of a hybrid powertrain. The system can select tractive torque from an internal combustion engine and/or from an electrical motor. Further, the description mentions using a traction motor to provide additional torque when an operator calls for more power in an attempt to eliminate “turbo lag”.
The above-mentioned system can also have several disadvantages. For example, the system apparently adjusts torque from a traction motor in response to an operator demand. However, if tractive motor torque is adjusted without regard to operating conditions of the turbo charger, the vehicle torque response may lag (follow behind) or lead (be ahead of) the compensation torque provided by the traction motor. This can result in a torque amount that may not match a desired torque amount and that may degrade vehicle drivability. Further, the torque provided by the traction motor may assist the internal combustion engine for a longer period of time than is desired. By increasing the traction motor assist time, additional energy may be consumed by the traction motor, thereby reducing the energy stored in the vehicle battery.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of controlling a hybrid powertrain having a compressor boosted internal combustion engine that offers substantial improvements.